This disclosure is based upon, and claims priority from French Application No. 99/03102, filed on Mar. 12, 1999 and International Application No. PCT/FR00/00555, filed Mar. 6, 2000, which was published on Sep. 21, 2000 in a language other than English, the contents of which are incorporated herein by reference.
The present invention relates to the manufacture of electronic devices having at least one circuit chip embedded in a support and electrically connected to interface elements by connection areas.
These electronic devices constitute for example portable devices such as smart cards, and more particularly cards capable of functioning without contact by means of an antenna integrated into the card, or electronic labels or electronic modules including an antenna.
Such cards are intended to perform various operations such as, for example, banking operations, telephone communications, identification operations, operations of debiting or reloading units of account, and all kinds of operations which can be performed at a distance by high-frequency electromagnetic coupling between a transmission/reception terminal and a card placed in the action area of this terminal.
The labels and electronic modules allow all kinds of identification operations.
One of the main problems which it is necessary to resolve in the manufacture of such devices is the connection of the antenna to the integrated circuit chip providing the electronic functioning of the device.
Another problem which it is necessary to resolve, in the case of a card or label, is the reduction of the thickness of the device to the maximum possible extent.
The classic constraints of mechanical strength, reliability and manufacturing cost must obviously be taken into account in this manufacture.
A known solution of the prior art, described in the PCI document WO 96/07985, for making the connection between the antenna and the integrated circuit chip, consists of forming metallic protrusions on two contact pads on the chip, and then connecting these protrusions to the ends of an antenna wire. In this case, the antenna wire is a copper wire formed on a substrate and the protrusions are applied to this antenna wire by hot compression.
However, the interconnection unit thus obtained has problems of mechanical strength and fragility under traction of the connection. This is because, when the chip is subjected to mechanical stresses, the protrusions suffer damage affecting the quality of the electrical connection. The mechanical stresses can even go as far as causing the rupture of the protrusions and consequently the pulling away of the chip. The contactless smart cards produced according to this prior method therefore have a relatively short life.
In another known solution of the prior art, the connection between the antenna and the chip is effected by means of conductive glue applied between the antenna and metallic protrusions formed on two contact pads on the chip. In this case, however, a significant excess thickness appears because of the presence of the glue and the protrusions. In addition, the manufacture of the card requires an additional step of dispensing dots of glue.
The protrusions, and where applicable the dots of conductive glue, have a not insignificant thickness which is added to that of the antenna and that of the chip, which increases the bulk of the interconnection unit obtained. However, it is sought to obtain an interconnection unit of very small bulk in order to produce an ultraflat contactless smart card, that is to say with a thickness less than the standard ISO thickness. The standard ISO 7810 corresponds to a card with a standard format 85 mm long, 54 mm wide and 0.76 mm thick.
In addition, the use of conductive glue during the connection of the chip to the antenna may, in certain cases, cause electrical malfunctioning in the chip in the event of pouring of the glue onto the sides of the chip.
The purpose of the present invention is to mitigate the drawbacks of the prior art.
To this end, the present invention proposes to manufacture an electronic device such as a contactless smart card, a label or an electronic module in which at least one chip is directly connected to an antenna by means of metallised protrusions embedded in the thickness of the antenna, at the time the chip is attached to the antenna.
In addition, the method according to the present invention proposes to transfer the chip to an insulating substrate and to package it so as to insulate its sides whilst leaving its contacts appearing on the surface.
The object of the present invention is more particularly a method of manufacturing an electronic device containing at least one integrated circuit chip connected to an antenna, characterised in that it includes the following steps:
transferring a chip into a recess provided in a support made of insulating material;
connecting the chip to an antenna by hot lamination of an insulating sheet carrying the antenna, the connecting pads on the antenna being placed opposite the connecting pads on the chip.
According to one characteristic of the present invention, the impression consists of a perforated insulating sheet, laminated or rolled on a second insulating sheet, the perforation having dimensions greater than those of the chip.
In a variant embodiment the impression is machined in the insulating material.
According to another characteristic, the method according to the invention also includes a step of insulating the sides of the chip.
According to one variant, the insulation of the sides of the chip is effected by distributing an insulating material filling the gap between the edges of the impression and the sides of the chip.
According to a variant embodiment, the insulation of the sides of the chip is effected by spraying an insulating material.
According to another variant, the insulation of the sides of the chip is effected by hot lamination of the material of the insulating support so as to form a melt in the gap between the edges of the impression and the sides of the chip.
According to this last variant, the step of protecting the sides of the chip and the step of connecting the chip to the antenna are performed during a single lamination.
According to another characteristic, the chip has metallic protrusions produced on each contact pad, the antenna being produced from a material able to be softened by thermocompression.
The metallised protrusions have a substantially conical shape.
According to one characteristic, the insulating sheets have dimensions greater than or equal to the format of the electronic devices to be produced, the insulating sheets being cut, after the step of connecting a plurality of chips to a plurality of antennae, in order to release a plurality of electronic devices.
According to another characteristic, the insulating sheets have dimensions equal to the format of the electronic device to be produced, a chip being connected to an antenna.
The electronic device to be produced is a smart card.
The electronic device to be produced is an electronic label.
The manufacturing method according to the invention has the advantage of protecting the sides of the chip during the interconnection step.
In addition, the method according to the present invention makes it possible to interconnect a matrix of chips to a plurality of antennae in a single operation. This is because it is possible to position a plurality of chips and a plurality of impressions in order to insert a large circuit or a plurality of circuits which are cut after the connection step.
In addition, given that the protrusions are embedded in the thickness of the antenna, the interconnection assembly formed by the chip and antenna has reduced bulk, which is very advantageous for producing an ultraflat electronic module.